Method of and apparatus for surface hardening metal articles



Feb. 24', 1942. v- SHQRTER A 2,274,005

METHOD OF AND APPARATUS FOR SURFACE HARDENING METAL ARTICLES Filed Jan. 13, 1959 4 Sheets+Sheet 2 60' A A 3/ fl\ J 55 I I A 67 a" m P".- mum l- H ,5

ATTORN EY Feb. 24,1942. A. E. SHORTER METHOD OF AND APPARATUS FOR SURFACE 'HARDENINGMETAL ARTICLES Filed Jan. 13, 1959 4 Sheets-Sheet 3 a I/ f V "L WM I v 4?) mm|um w----. INVENTOR ALBERT E. SHORTER ATTORNEY Feb- 2 9 7 A. E. SHORTER ,00

' METHOD OF AND APPARATUS FOR SURFACE HARDENING METAL ARTICLES,-

. Filed Jan. 13, 1959 4 Sheets-Sheet 4 "qz-q L- T, I

I? l l l l/j' u I iNVENTOR ALBERT E.SHORT,ER'Y

ATTORNEY Patented Feb. 24, 1942 I METHOD or AND APPARATUS FOR SURFACE HARDENING METAL ARTICLES 'Albert Edward Shorter, Sheflicld, England, as-

signor to The Linde Air Products Company, New York, N. Y., a corporation ofOhio Application January 13, 1939, Serial No. 250,739

. In Great Britain January 14, 1938 6 Claims. (01. 148--19.9)

This invention relates to the surface hardening of metal articles, and more particularly to the hardening of profiled surfaces ofmetal arti T cles such as plates, cams, sprockets, gears, etc.

As used herein profiled surfaces refers to ec- I centric projections, indentations, or similar curved details of plates or cams; or teeth of sprockets or gears, or the like, but not to surfaces of uniformly cylindrical metal articles, such as shafts.

According to prior methods of hardening articles suchas gears, a heating flame followed by a quenching medium is directed against successive portions of the width of each tooth of a gear, each tooth being hardened individually and the teeth of the entire gear 'being hardened in succession. Difiiculty is, however, experienced in cases where it is desired to harden the entire side of each gear tooth down to the root, or to harden each tooth across its full width but only over selected portions of the face or flank. (The face of a gear tooth, is that portion of the side extending from the top to the pitch circle or pitch line, and the flank of a gear tooth is that portion of the side extending from the pitch circle or pitch line to the root.)

Among the objects of this invention are to provide a novel method of hardening profiled surfaces of metal articles wherein successive pore tions of the periphery of such articles are treated; to provide a novel method of hardening profiled lsurfaces of metal articles wherein a plurality of similar details are expeditiously treated;

to provide such a method in which a heating medium and quenching medium may be directed against a detail of a profiled surface across the full width thereof; and to provide apparatus particularly adapted to carry out the method of this invention. Other objects and novel features will become apparent from the followingdescription and accompanying drawings, in which:

Fig. 1 is a diagrammatic plan view of apparatus constructed in accordance with this invention, and arranged for hardening semi-circular projections of a metal article;

Fig. 2 is a diagrammatic plan view of the apparatus of Fig. 1, arranged for hardening semicircular indentations of a metal article;

Fig. 3 is a side elevation of the apparatus of Figs. 1 and 2;

Fig. 4 is an end elevation, partly in section, of the apparatus of Fig. 3;

Fig. 5 is a partial side elevation showing in greater detail a portion of the apparatus of Figs.

3 and 4; and

Fig. 6 is a partial'end elevation showing in greater detail a second portion of the apparatus of Figs. 3 and 4.

According to this invention, successive portions of curved details of a profiled surface of a metal article are treated by effecting a relative rotation between the article and a heating unit, or

' other suitable source of high temperature heat,

about an axis coinciding with the center of curvature of each detail, the distance betweenthe surface of the detail and the heating unit or source of heat being thereby automatically maintained constant. The heating unit is preferably one which is adapted quickly to heat successive portions offthe surface of each detail to a temperature at or above the critical range, and in additionfa quenching or cooling unit is preferably associated with the heating unit in such a manner that a quenching and cooling medium is directed against successive heated portions so as to harden the same.

The principles of this invention may b utilized with particular advantage in hardening the teeth of sprockets, where the opposed. flanks of adjacent teeth and the root portion joining the two flanks is approximately semi-circular in shape, the center of the semi-circle lying on or .being closely adjacent the pitch circle. In such a case, the heating unit is maintained approximately at the center of the semi-circular detail, and the sprocket rotated relatively to the heating unit about an axis coinciding with this center. A uniform distance between the surface of thesemi-circular detail and the heating unit is thereby maintained throughout the entire path of traverse.

Apparatus constructed in accordance with the principles of this invention, and particularly adapted to carry out the method of this invention may comprise a rotatable carriage adapted to support the metal article in such a position that the center of curvatur of a detail to be hardened'may be located co-axially with the axis of rotation of the carriage, a heating unit or device and a suitable support for locating the heating unit in spaced relationship with the surface to be hardened, and suitable means for effecting a relative rotation between the article and the heating unit about the center of curvature of the detail to be hardened. In addition, one or more quenching nozzles or devices may, in the usual manner, be associated with the heating unit.

The rotatable carriage may, comprise a machine slide mounted uponand extending dialocating the heating unit in spaced relationship with respect to the surface of a detail to be hardened, a bracket overhanging the rotatable carriage and provided with suitable horizontally and vertically adjustable supports may be employed. I

More specifically, apparatus utilized in carrying out the-method of thi invention, as illustrated in Fig. 1, may comprise a machine slide l mounted diametrically upon a horizontal turntable II, which is rotatable about a vertical axis. 12. A metal article, such as a gear or sprocket I3, having a plurality of semi-circular projections I4, is placed upon slide III, with the axis 3 of the gear or sprocket passing through the central longitudinal axis of the slide. The slide is adjusted radially with respect to the turntable by means of a hand wheel l5 so that the center of curvature of one of the semi-circular projections I4 coincides with the axis 12 of turntable II.- A heating burner I6 and associated quenching nozzle 11 are then positioned at a suitabledistance from the surface of the detail to be hardened. Upon rotating the turntable II, in the direction of the arrow of Fig. 1 and through 180 about its axis [2, while maintaining burner I 6 and quenching nozzle l1 in fixed position, the entire semi-circular surface of a projection I4 is progressively treated by the heating and quenching devices, and a uniform hardening is effected. When the treatment of one projection has been completed, the article [3 is rotated about its axis 16 to bring another projection into position to ,be treated. To hold each projection or detail accurately in the correct position with respect to the heating and quenching devices, a spring controlled detent l9 engaging the metal article 13 between two projections 14 spaced from the projection under treatment is utilized.

In Fig. 2, the apparatus of Fig. l is shown when utilized in the treatment of a metal article, such as a sprocket. 13', having semi-circular depressions 14, the surfaces of which are to be hardened. In this instance, sprocket I3 is adjusted radially with respect to turntable II so that the center of curvature of one of the semicircular depressions l4' coincides with the axis l2 of turntable H, and the end of the burner nozzle of the heating unit 16 is positioned at axis 12. Rotation of turntable I I, in the direction of the arrow of Fig. 2, will cause the surface of the semi-circular depression to be progressively hardened by the action of burner 16 and quench.- ing nozzle 11.

As shown in Figs. 3 and 4, the machine slide 16 and turntable H may be supported by a central vertical spindle 20. Spindle 20 extends downwardly through a circular trough 2|, which is adapted to collect the quenching liquid after impingement upon the surface of a detail being hardened, and trough 21 is mounted upon a machine bed 22, which houses the driving mechanism for rotating turntable ll. Trough 2 I' may be provided with a discharge pipe 2ia for carrying the quenching liquid down to a sump 23.

The driving mechanism is designed for optional manual or power-operated drive. For manual operation, a shaft 24 extending through machine bed 22 and provided at its outer end with a hand wheel 25 is utilized. A bevel gear 26 is secured to shaft 24 at its inner end, and bevel gear 26 meshes with a second bevel gear '21, in turn secured to vertical shaft or spindle 20 in order to effect rotation of turntable II.

For power-operated drive, a shaft 29 of an electric motor 28, bolted to machine bed 22, is coupled through reduction gearing 36 and a variable speed drive to a worm 3| which engages a worm gear 32. Worm gear 32 is mounted on a vertical stub shaft 33 disposed directly beneath vertical spindle or shaft 20 and stub shaft 33 drives spindle 20 through a dog clutch 34.

Parts of the mechanism for disengaging clutch 34 when the manual drive is to be used have been omitted from Fig. 4, for the sake of clarity, but are shown in greater detail in Fig. 5.

Referring now to Fig. 5, the upper half or element of dog clutch 34 is provided with a collar 35, and a fork 36 embraces collar 35. Fork 36 is secured to a vertical shaft 31, disposed alongside spindle 20, and shaft 31 is slidably mounted in a guide bracket 36 secured to the machine bed. Shaft 31 is connected through a toggle linkage system 39 to a foot pedal 46, depression of which serves to disengage clutch 34, while a spring 41 holds clutch 34 in engagement when pedal 46 is not depressed.

The reduction gearing and variable speed drive are illustrated more clearly in Fig. 6. Secured to the end of motor shaft 29 is a worm 42, which engages a worm gear 43 secured to a spring loaded vertical shaft 44, provided at its lower end with a friction disc 45. Friction disc 45 is pressed by the spring loaded shaft 44 into engagement with a friction wheel 46 splined on a shaft 41, worm 3| being mounted on the opposite end of shaft 41. For varying the speed of drive, or for reversing the direction of drive, friction wheel 46 may be moved radially with respect to friction disc 45 along splined shaft 41. To effect such adjustment, a fork 48 which fits over friction wheel 46 is secured to an actuating rod 49, rod 49 being coupled through a link 56 and a screw threaded bearing 5| to a screw 52. Screw 52 is provided with a hand wheel 53, which may be conveniently located close to hand wheel 25. as illustrated more clearly in Fig. 3, and a switch I 54 for controlling motor 28 may also be conveniently mounted on machine bed 22 alongside hand wheels 25 and 53.

For readily locating the heating and quenching devices with respect to the surface of a detail to be hardened, a vertical supporting pillar 55 carrying a horizontal arm 56 is disposed alongside the machine bed. The arm 56 is pivotally mounted for movement in a horizontal plane in a bracket 51, bracket 51 being slidably mounted on pillar 55, and a clamp 56 being adapted to secure bracket 51 in any desired position. A weight 59 balances arm 56, to insure easy vertical adjustment of bracket 51 and arm 56.

A carriage 60 is slidably mounted on arm 66, and a clamp 61 is utilized in looking carriage 66 in any desired horizontal position. One end of a bracket 62 is secured to heating unit 16, and the other end of bracket 62 is rotatably mounted on a vertically adjustable shaft 63, a clamp 62' being provided to permit bracket 62 to be locked in any desired radial position on shaft 63. Vertical shaft 63-is slidably mounted at the end of a horizontal bar 64, in turn slidably mounted on carriage 60. Relatively fine adjustment of the position of the heating unit and shaft 63 in a vertical direction may be effected by a control handle 65, while relativelyflne adjustment of the tance between the heating unit and the surface. heating unit and bar 64 in a horizontal direction Rotation of bracket 62 may be eifected manually, may be effected by a hand wheel 6'. f Flexible or may beeflected automatically in any suitable conduits 61 for supplying suitable gases to heats manner. when treating details which correing unit I6 are carried over a guide pulley 88 6 spond in shape to a portion of acircle,-such as mounted on the end of arm ,and are connected. semi-circular projections or indentations, the with a suitable source or sources of supply of a necessity for rotating bracket 62 and heating unit combustible gas and a combustion supporting ll of course does not arise, and in such instances gas, such as acetylene and oxygen. One or more bracket 62 may be locked on shaft 63 by clamp 62' 'quenchins lOZ es, such as .quenching'nozzle ll 10 after initial positioning.

of Figs. 1 and 2, may be provided alongside the Should it be desired to harden only a portion heating, unit' and secured thereto or to bracket of a curved surface, suitable mechanism may be '62, as shown, and a flexible conduit "for supprovided for disconnecting the supplyof ases to plying a quenching medium to the nozzle or the heating unit while those portions which are nozzles may also be carried over guide pulley 68. to-remain unhardened are traversed by the heat- After the metal article having details to be ing unit. hardened, such as a sprociret It, is mountedon In order to re-use the quenching liquid in case 111180111118 slide III in such a manner that the suchisdesirable, suitable meansmaybeprovided center of curvature of the detail coincides with in connection with sump 23 in order to convey the the axis .of turntable II, the heating unit and liquid back to the quenching nozzles. Such associated quenching nozzles are placed in the means mayconveniently be operated by motor 28.

desired'proximity to the surface of the detail to Suitable mechanism may be provided to stop I be hardened by adjustment of control handle 65 motor 28 as soon as a detail to be hardened has and hand wheel 66. Motor 28 is then started so been treated, and such mechanism may also be that turntable II will be rotated and the curved 25 coupled with suitable means for controlling the surface of the detail to be hardened will 'thereflow of gases to ,the heating unit so that the p n be pmsressively h rdened by the heating applicationof the heating medium may be termiand quenching units while the latter remain at nated simultaneously with the stopping of the a uniform distance from the surface. motor.

- Rotation of turntable II and the metal ar- 80 It will be understood that the apparatus may e e c w pr v de f r. the treatment he so constructed that the article to be treated of one semi-circular detail, so that after the may be mounted for rotation about a horizontal turntable has rotated through this angle, the axis instead of a vertical axis, or about an axis motor 28 may be stopped and'the article moved inclined at any other convenient angle. It also about its own axis through the space of one dewill be understood that the heating medium may tan the hilldenillfl Operation en being be not only a combustible mixture of gases, such repeated. To avoid the necessity of bringing the as oxygen and acetylene, but also any other suitturntable back to'its initial position before comable type of heating medium adapted to heat sucmencing the treatment of a succeeding detail in cessive portions of a detail to be hardened. It will cases where such details are identical with 'one 60 b further understood that various other changes another. the dir i of rotation of spindle 20 [may be made which will not depart from the ybe reversed by moving friction wheel 46 to spirit and scope of this invention.

the other side of thecenter of disc II by hand What is claimed is:

wheel n t n spindle 20 and the 1. A method of surface hardening a plurality metal article in such reverse direction, to effect of curved peripheral details of a profiled surface qu n nozzle l7 Sh l d b P ti n t of a metal article, all of said details lying subonno i e de f a in b n r as at H in stantially in the same plane and each of said de- Fig. 1, or a second quenching nozzle providedon t il conforming substantially to a portion of a the'opposite sideoi' burner I. circle of revolution with the axes of said details The heating unit used. of ur e. sh ifld cover 50 located substantially equi-distantly from a comthe full-width of the surface to be hardened. mon center disposed in saidplane, such method where the surface of the detail to be hardened comprising mounting th article with an axis of does notconstitute part of a'smooth circle, such rotation extending through said common center,

a s ar tmwhose surface normally correand also with a second axis of rotation extending 9 1 to 8 p r on 1 n i volllte Gi -We. er through the axis of revolution of one of said dewill be no ,exact center of curvature-of the detail. tails; positioning a source of high temperature In such a case, the article is so placed that the heat in relatively fixed position and in operative axis of turntable ll coincides with an approxirelation with respect to the detail whose axis matecenter of curvature ofthe detail, that coincides with the second center of rotation; oin most nearly l fl im f m 511 P in on eileeting'rotation of said article about said second the curve of the surface. But even when axis i2 nter so as to heat su cessive surface portions coi id s wit su h a 'anproximate cente of of said detail; effecting rotation of said article curvature; all P i s on the surface will not be about said axis extending through said common located equidi tly from axis l2. Consequentcenter,"so as to place a second detail in such a -17, a8 turntable ll o ates, the heating medium position that its axis will coincide with said w be directed n rmally aga st th surffloe second center of rotation; effecting rotation of of any such details, which are eccentric. I-Iowsaid article about said second axis so as to heat ever, the heating unit." is, as previously desuccessive surface portions of said second detail;

' scribed, rotatably mounted on vertical shaft 83, and intermittently rotating ,said article about the longitudinal axis of shaft 03 preferably passsaid commoncenter and about said second center ing through the end of the nozzle of heating so as to treat successive detailsina similar manunit 16. By suitably rotating bracket 62 about ner while maintaining said source of high temshaft 63 during treatment, the application'of the perature heat in relatively fixed position.

h tin flame ma be maintained normal to.the 2. A method of hardening a plurality of curved 'sii fac being tre ted without changing the disdetails of a profiled surface of a metal article; in

which high temperature heat is applied to the surface of each detail so as to heat the same to a temperature at or above the critical range, such method comprising directing a high temperature heating medium substantially normally against the surface of one of said details; during the application of heat effecting rotation of said metal article about an axis coinciding with the approximate center of curvature of the detail being hardened; rotating said article about its own'axis so as to place a second detail in position for treatment; rotating said article about an axis coinciding with the approximate center of curvature of said second detail, but in a direction opposite to that in which rotation was effected during the treatment of the first detail hardened; and similarly rotating said body about its own axis and then about an axis coinciding with the approximate center of curvature of each subsequent detail to be hardened.

3. A method of hardening in succession a plurality of similar curved details of a profiled surface of a metal article, each of such details having a center or approximate center of curvature located at substantially the same distance from the axis of said article, such method comprising mounting said article for rotation about its own axis and also for rotation about a second axis coinciding with the center or approximate center of curvature of a detail to be hardened; intermittently rotating said article about its own axis to cause the center or approximate center of curvature of successive details to coincide with said second axis; mounting a heating and quenching unit in spaced operative relationship with respect to a detail whose center or approximate center of curvature coincides with said second axis; intermittently rotating said article about said second axis; and maintaining said heating and quenching unit in a relatively fixed position during such intermittent rotation of said article, both about its own axis and about said second axis.

4. Apparatus for hardening a plurality of curved details of a profiled surface of a metal article, each of such details conforming substantially to a portion of a circle of revolution and the axes of such circles of revolution being located substantially equi-distantly from a common center, said apparatus comprising a rotatable carriage provided with means for supporting the metal article in such a position that the center of curvature of a detail to be hardened coincides with the axis of rotation of the carriage; means for reversing the direction of rotation of said carriage; means for supporting a heating unit in spaced relationship with respect to the surface of the detail to be hardened; means for effecting a relative rotation between the article and said heating unit about the center of curvature of such detail so as to heat successive portions of said surface and maintain said heating unit at a uniform distance from the surface during such heating; and means for effecting a relative rotation between said article and said heating unit about said common center so as to place successive details to be hardened in spaced relationship with respect to said heating unit.

5. Apparatus for hardening in succession a plurality of curved details of a profiled surface of a metal article, such details having only an approximate center of curvature, such apparatus comprising, in combination, a rotatable carriage; means adjustable radially with respect to the axis of rotation of said carriage for rotatably supporting said article on said carriage; means for supporting a heating unit in spaced relationship with respect to the surface of a detail to be hardened; means for rotating said carriage so as to effect a relative rotation between the article and the heating unit in order to cause successive portions of the surface of a detail being treated to be heated, said heating unit being rotatably mounted so as to permit a heating medium to be directed normally against the surface during the application of heat without substantial alteration in the distance between the surface and the heating unit; and means for registering in succession each of such details to be hardened in operative position with respect to said heating unit and with the approximate center of curvature of each detail ,so registered coinciding with the axis of rotation of said carriage.

6. Apparatus for hardening a curved detail of a profiled surface of a metal article, comprising a rotatable carriage; means adjustable radially with respect to the axis of rotation of said carriage for rotatably supporting said article on said carriage; means for rotating said carriage; means for reversing the direction of rotation of said carriage; means for applying high tempera- 

